By Josh Nathan-Kazis

Merck shares were rising early Tuesday in response to positive results from a trial of the heart drug that the company is counting on for much of its growth.

Patent protection on Keytruda, the cancer treatment that accounts for nearly half of Merck's revenue, is nearing its end, so the company is rushing to buy and develop alternatives. It has turned significant focus to the heart drug Winrevair, which is anticipated to be a top seller.

Analysts now expect Winrevair sales to surpass $5.5 billion in 2030, according to FactSet, up from just over $400 million last year.

The Food and Drug Administration approved Winrevair in March 2024 as a treatment for pulmonary arterial hypertension, a form of high blood pressure. Now, the company is seeking to expand Winrevair's approval to include other, related conditions.

On Tuesday, Merck said that one of its continuing Phase 2 trials of Winrevair had been successful, and that the company would proceed with a Phase 3 study.

The trial, called CADENCE, tested Winrevair in patients with heart failure with so-called preserved ejection fraction who had developed what is known as combined post- and precapillary pulmonary hypertension.

That is a mouthful. Essentially, the company was testing whether Winrevair could ease the transition of blood through the lungs to the heart in certain patients with heart failure who have a form of high blood pressure.

Merck said that the trial had shown a "statistically significant and clinically meaningful reduction" in a measure of cardiac and blood vessel function called pulmonary vascular resistance. Lower results point to a healthier system. The company provided no detailed data.

Shares were up 3.4% to $95.97 on Tuesday morning.

Cantor analyst Carter Gould wrote early Tuesday that the news seemed good for Merck, but that anything less than a positive outcome would have been taken badly by investors.

Gould wrote that investors are attributing as much as $2 billion of the $8 billion to $8.5 billion peak sales estimated for Winrevair to indications other than the one for which the drug is already approved. The bulk of that is in patients with heart failure with preserved ejection fraction.

Anything short of a successful trial and progression to Phase 3, Gould wrote, "would have been viewed negatively -- particularly with the estimates already ascribed to Winrevair."

Merck shares are down about 6% this year as a result of growing anxiety about the outlook for the company after patent protection for Keytruda expires in 2028. The company's third-quarter results didn't help: Winrevair sales missed estimates.

Last week, Merck announced a deal to buy the biotech Cidara Therapeutics for $9.2 billion in a separate effort to fill the revenue gap that Keytruda will leave. Cidara is developing a new flu prevention drug.

Write to Josh Nathan-Kazis at josh.nathan-kazis@barrons.com

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November 18, 2025 10:26 ET (15:26 GMT)

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